In the field of heating and air conditioning, it has long been known that the use of exhaust vents frequently creates negative pressure within the heated building, unless adequate provisions are made to provide a sufficient supply of outside air to compensate for the exhaust discharge. This problem is frequently experienced in industrial plant settings, where negative pressure within the building can result in various problems such as backdrafts in flues and ventilators, excessive drafts through doors and windows, and dispersal of contaminants throughout the building. A common solution to the problem is the use of make-up heaters, which provide an inflow of fresh air heated to a desired delivery temperature roughly equivalent to the comfort level for the space heating system in the building.
Make-up heaters are frequently gas fired, having a plurality of burners disposed upstream of a squirrel cage blower or other type of fan. Cold outside air is drawn over the burners and heated to the desired temperature, then discharged into the building by the blower. A typical electronic ignition system incorporated in a conventional make-up heater includes a spark generator and a spark plug disposed in the vicinity of the burners. With traditional spark systems, the spark is generated in mid-air, making it very susceptible to air and gas velocity which tend to extinguish the spark. Furthermore, the electrodes on conventional spark plugs may become warped with extended usage and deteriorate over time, rendering the spark and its location unreliable for efficient ignition. The problems with conventional spark plugs are compounded when the system is used in extremely cold and/or moist air. Accordingly, it has been found highly desirable to devise an ignition assembly for use in make-up air heaters which solves the aforementioned problems which may be encountered in conventional spark systems.